Rocker arm with integral internal oil passages

ABSTRACT

A rocker arm and method for manufacture is provided whereby the rocker arm is manufactured in two halves generally symmetric to a central plane. The mating surface of one or both rocker arm halves incorporate grooves which upon assembly provide passageways which may follow any desired pathway for lubricant and or afford a reduction in mass and/or an increase in structural stiffness. The two halves are preferably joined together by metallurgical brazing or by other chemical or mechanical means.

FIELD OF THE INVENTION

The present invention relates to a rocker arm and method for making a rocker arm for an internal combustion engine having internal oil passages. More particularly, the invention relates to an improved rocker arm having internal oil passages formed by joining pre-fabricated sections that have oil passages as an integral feature of at least one of the sections.

BACKGROUND OF THE INVENTION

Conventional methods for manufacturing rocker arms generally involve stamping or casting procedures. The formed pieces are thereafter processed to remove material by machining e.g. drilling, milling, etc. to form oil passages in the rocker arm. Such methods by machining, drillings, milling, etc. require the removal of material to create the necessary oil passages. Additionally, passages formed in that manner are often less precise in dimensions and location. Also, prior art drilling or machining of oil passages, as a practical matter, must comprise a straight line and be of a size compatible with the drilling process and cannot take the form of a “worm” groove formed so as to provide the optimum advantage. Additionally, deeper holes, e.g. those in excess of about 10 drill-diameters deep, require the use of slower, relatively costly drilling process i.e., gun drilling. A method for production which pre-fabricates sections and the resulting product with precisely formed and located oil passages and joins such sections to form a finished rocker arm would be advantageous in cost and time savings.

SUMMARY OF THE INVENTION

The novel rocker arm of the invention is characterized by joining the pre-fabricated sections of sintered metal particles, generally two halves that are symmetrical to a central plane and wherein the mating surfaces of one or both halves incorporate grooves which upon assembly form one or more passageways for oil. The resulting product results in a significant reduction in mass and is found to produce an increase in structural stiffness. The pre-fabricated sections, preferably of powdered metal composition, are joined together by any convenient known technique such as by metallurgical brazing or by chemical or mechanical means.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a perspective view of the rocker arm assembly formed by joining two separated preformed parts as contemplated by the invention mounted on a rocker shaft (not shown) and an hydraulic lash adjuster cartridge installed therein.

FIG. 2 is a perspective view of two pre-fabricated mirror-image sections of the rocker arm of the invention.

FIG. 3 is a perspective view of the assembled sections show in FIG. 2.

DETAILED DESCRIPTION OF THE INVENTION

The rocker arm of the invention comprising the pre-fabrication of separate mating sections, preferably two sections, is manufactured conveniently such as by furnace brazing together the sections, preferably formed of a powdered metal and containing integrally formed grooves in one or both mating sections. Additional machining or drilling to form internal passageways is avoided.

The metal is atomized by methods in which a stream of molten metal is struck with air or water jets and the formed metal particles are collected, sieved and annealed. In processing, the powdered metal particles, including mixtures of different metals, are shaped into the desired suitable form such as by flowing the metal powder usually at room temperature into a die cavity shaped as the finished part, and then applying pressure from above and below to form a compact. After ejection from the die, the compact is heated (sintered) to form a coherent mass with the configuration of the original die and properties related to the metals used. The pressure applied affects the density as well as the strength of the formed piece; the greater pressure the higher the strength. A low density porous compact may be formed by pouring the powder into a die and then heating it without first applying pressure. The shape and size of the die cavity can be exactly as required by the finished part. However, if desired, this invention contemplates the use of any suitable metal or metal alloy powder and preferable powders of iron or iron alloys.

Referring to the drawings, FIG. 1 illustrates an essentially completely assembled rocker arm 20 comprising the rocker arm body 22, a hydraulic lash adjustment cartridge 24, roller bearing 26, and roller bearing axle 28.

Referring to FIG. 2 there is illustrated two sintered metal pre-fabricated sections 30 and 32 which when sintered together form the rocker arm body 22. Rocker arm section 32 incorporates lubricant pathway grooves 34 and 36 which when the two sections 30 and 32 are combined, i.e. covered by surfaces 44 and 46 during assembly, form oil passages which communicate lubricating oil provided by the rocker shaft (not shown) installed in openings 38. The pre-formed lubricant pathways 34 and 36 may follow any desired path. The circuitous path of the groove 34 is facilitated by means of the two rocker arm sections which further permits openings 48, 50, and 52 which reduce mass and rotational inertia and permits structural beam element 42 which increases the stiffness of the rocker arm body shown in FIG. 3.

Although the invention has been described with respect to a preferred specific embodiment, many variations and modifications will become apparent to those skilled in the art. It is therefore the intention that the claims be interpreted as broadly as possible in view of the prior art to include all such variations and modifications. 

1. A method of making a sintered metal rocker arm from complimentary pre-fabricated mating sections of metal powder wherein at least one of said sections contains an integral formed lubricant passageway, and bonding said section to form the rocker arm product containing therein the integrally formed internal passageway.
 2. The method of claim 1 wherein the rocker arm is made by joining two complimentary half-sections.
 3. The method of claim 2 wherein the lubricant passageway is contained entirely within one or more of the pre-fabricated sections.
 4. The method of claim 2 wherein the lubricant passageway is formed when the complimentary sections are mated and bonded together.
 5. The method of claim 1 wherein the two complimentary half-sections are comprised of a powdered metal alloy.
 6. The method of claim 1 wherein the section are comprised of powdered metal selected from iron and iron alloys.
 7. The method of claim 1 wherein the sections are bonded by metallurgical brazing.
 8. The rocker arm produced by the method of claim
 1. 9. The rocker arm produced by the method of claim
 4. 10. The rocker arm produced by the method of claim
 6. 